A computer-driven display system is typically composed of one or more graphics output adaptors connected to a host computer and a set of displays that are connected to the graphics adaptor(s). The mapping between multiple display devices and the graphics adaptors is typically determined through the EDID protocol that specifies that a display is connected and various attributes of that display. However, this protocol does not (and cannot) automatically discover the mapping between graphics adaptor output port and the display configuration. This mapping is important so that displays render the appropriate portion of a contiguous display. This mapping is typically defined by a user through a interactive software interface.
Consider the case where a host computer contains a single graphics adaptor with that has two output ports, Output1 and Output2. A user may connect a cable from each output to a respective display monitor, Monitor1 and Monitor2. At connection time, EDID protocols determine the video resolution, supported clock timings, etc., for each of the displays. Assume that Monitor1 is connected to Output1 and Monitor2 is connected to Output2. If the user places Monitor2 to the left of Monitor1 for viewing, the graphical system should render the left side of the virtual display on Monitor2 while the right side of the virtual display should appear on Monitor1.
In previous systems, the initially unknown mapping from the output of the graphical adaptor to the virtual screen is typically managed by either the host PC graphics driver or the operating system, and is determined via user interaction. This mapping was typically accomplished through a two-step process. First, the graphics adaptor detects that a device is connected and determines its resolution, and then a user interacts with software to inform the graphics adaptor about the geometric layout of the display devices. This step was necessary to establish a mapping from the graphical output to the portion of the virtual screen that is rendered from that output.